Exemplary embodiments of the present invention relate to a method for operating a brake assist device for a vehicle and to a brake assist device.
German Patent document DE 102 58 617 A1 discloses a device and a method for triggering an automatic emergency braking process of a vehicle for avoiding a collision of the vehicle with a vehicle in front or for reducing the consequences of a collision, wherein a driver alarm is triggered if at least one predetermined alarm condition is fulfilled. The fulfillment of the alarm condition indicates that, on the basis of the momentary driving situation of the vehicle with a calculated acceleration of the vehicle and/or a calculated relative acceleration between the vehicle and a moving vehicle in front taken into account and on the basis of a predetermined emergency braking deceleration, the automatic emergency braking process is triggered when a predetermined warning time period has passed. The emergency braking process is triggered to achieve a predetermined target relative speed and/or a predetermined target safety distance between the vehicle and the vehicle in front once the automatic braking process is finished. A point in time is defined, which is the latest time at which full braking must be initiated in order to avoid a collision. The warning is then triggered if an interval for action up to this point in time falls below the predetermined warning time period.
PCT International Publication WO 2006/072342 A1 discloses a collision avoidance or collision consequences minimizing device and a method for operating a collision avoidance or collision consequences minimizing device of a vehicle. An existing driving distance between the vehicle and a potential collision partner is detected and a first alarm function and/or information function is activated upon reaching a first threshold value. Upon reaching a second threshold value an automatic partial braking is triggered in combination with at least one other safety measure. A partial braking is a braking with a deceleration that is less than the deceleration achievable with a full braking.
Exemplary embodiments of the present invention provide an improved method for operating a brake assist device for a vehicle and an improved brake assist device for a vehicle.
In a method for operating a brake assist device for a vehicle, an assist function is effected on the basis of a distance of the vehicle from an object in front of the vehicle and absence of driver action, in particular absence of braking and/or steering action, in particular the absence of braking and/or steering action on the part of the driver, by which the latter could reduce the hazard of a collision with the object, wherein as an assist function a warning indication is generated and/or a braking of the vehicle is automatically initiated.
A brake assist is understood to mean an active intervention in the forward control of the vehicle, in particular a control of the brake system of the vehicle, as well as an emission of visual, haptic, and/or acoustic indications which inform the driver that an intervention on the driver's part in the forward and/or lateral control of the vehicle, i.e., driver action, is required in order to avoid a collision of the vehicle with an object or at least reduce the consequences of such a collision.
According to the invention, a classification of a road on which the vehicle is being driven is carried out and the assist function is only effected if a trigger release condition dependent on the classification is fulfilled. The performance of the assist function is thus permitted or prevented on the basis of the classification. In a particularly advantageous manner, an operation adapted to the current environment (surroundings) of the vehicle is always achievable. In particular because of the adaptation of the trigger release condition to the classification of the road, accidental triggerings of the brake assist device induced by the detection of roadside structures or roadside objects such as reflector posts, guard rails, and traffic signs are avoided or at least significantly reduced. Such roadside structures and roadside objects generally depend upon the type of road, and the adaptation of the trigger release condition to the classification of the road takes them into account for triggering the assist function.
In an embodiment of the method according to the invention, the classification of the road involves a division into at least two classes, wherein the road is assigned to a first class as a highway-like road type or to a second class as a non-highway-like road type. The differentiation between the highway-like road type and the non-highway-like road type is particularly easily carried out and enables a simultaneous adaptation of the trigger release condition to the road type such that an effective and safe controlling of the brake assist device is achievable.
In an appropriate manner, the road type is determined with the aid of a number and/or width of marker lines delimiting the lane of the vehicle and/or with the aid of a width of the lane and/or from map data of a digital road map. This determination is particularly easily and effectively carried out and the respective road type can be determined with certainty.
In an improvement of the assist function, the trigger release condition is pre-specified such that it represents less of an obstacle to the execution of the assist function on a road assigned to the first class (i.e., a road classified as a highway-like road) than on a road assigned to the second class. The warning rate and/or the brake intervention rate is thus reduced on, for instance, rural roads and in developed areas (in other words, on non-highway-like roads) and unnecessary interventions of the brake assist device are avoided. On the other hand the full performance capacity of the brake assist device is ensured on highway-like roads such as two-lane expressways and motorways.
According to a particularly advantageous embodiment of the method according to the invention, the surroundings of the vehicle are monitored and a curvature of the road and/or a transverse offset of the object in front of the vehicle and/or a change in the transverse offset are detected as environment parameters and, for verifying the trigger release condition, in each case compared with a threshold predetermined on the basis of the classification of the road. Transverse offset of the object is understood to mean a lateral distance of the object from a longitudinal axis of the vehicle. The change in transverse offset refers to a change in the lateral distance that has taken place since the object was initially detected. The selection of the trigger release condition on the basis of the environment parameters leads to a further improvement in the functionality of the brake assist device, since the actions that are performed are adapted to the ambient situation of the vehicle. For example, a full braking on a curve with a sharp bend is thus avoided in order to prevent under- or oversteering or swerving of the vehicle.
Particular preference is given to additional selection of the respective escalation stage of the assist function on the basis of the classification of the road on which the vehicle is being driven. This selection of the escalation stage on the basis of the classification results in a control of the assist function adapted to the respective surroundings of the vehicle such that a hazard resulting from an automatic braking process posed to other traffic participants behind the vehicle is minimized, and thus even greater traffic safety is ensured.
In order to provide an assist function adapted to the current situation at all times, a visual and/or an acoustic alarm is/are emitted as a warning indication in a first escalation stage, an automatic partial braking is carried out as a haptic alarm in a second escalation stage, and a full braking is carried out as a braking process in a third escalation stage.
The first and second escalation stages of the assist function are preferably only performed if the object in front of the vehicle to which the assist function is supposed to react is stationary or moving in the same direction as the vehicle, i.e., is traveling in front of the vehicle. The third escalation stage is preferably only performed if the object is traveling in the same direction as the vehicle. Depending on the situation, the driver of the vehicle is thus able to avoid a collision with the object, in particular another moving vehicle ahead of the vehicle, by effecting a braking and/or an evasive maneuver. In the absence of driver action (i.e., should the driver not intervene), the collision with the object can be avoided, or at least the severity of the collision and the resulting consequences reduced, by the partial braking and/or full braking. Preferably, a full or emergency braking is not performed with stationary objects, in order to avoid triggering full braking for objects that cannot be clearly identified, in other words objects for which it cannot be determined with certainty whether they are in the road or next to the road. So-called unnecessary full braking is thus avoided when, for example, the vehicle is going around a curve and objects on the side of the road with no true speed of their own such as trees, plants, and roadside structures are detected.
Further, only those objects in front of the vehicle that are in the same lane as the vehicle are accounted for. The course of the lane and the position of the object in relation to the lane can be determined with the aid of, for example, a video-based lane detection system.
It is thus possible to prevent accidental triggerings of the brake assist device due to objects, in particular other vehicles that are not traveling in the same lane as the vehicle. In particular, accidental triggerings due to objects in the oncoming traffic flow relative to the vehicle are avoided.
A brake assist device for a vehicle includes a monitoring unit for detecting the distance of the vehicle from an object in front of the vehicle, another monitoring unit for detecting the action of the driver of the vehicle, and a control unit for effecting an assist function on the basis of the detected distance and the detected driver action, wherein the assist function includes at least the generation of a warning indication and/or the initiation of an automatic braking process of the vehicle.
According to the invention, an environment monitoring device captures environment data related to a road on which the vehicle is being driven, wherein the control unit comprises a processing unit coupled with the environment monitoring device, by means of which unit the road on which the vehicle is being driven can be classified with reference to the captured environment data. The control unit is configured to execute the assist function on the basis of the classification of the road on which the vehicle is being driven. A distinguishing characteristic of the device is its simple construction. The brake assist device of the invention is particularly easily implemented, especially in vehicles that are already equipped with an environment monitoring device and a brake assist device. A monitoring device of a lane keeping assist device is particularly well-suited as an environment monitoring device.
Corresponding parts have the same reference signs in all of the Figures.